...

cxx/mcc_traits.h

@@ -131,4 +131,45 @@ template <typename T>
 using mcc_func_arg1_t = typename mcc_func_traits<T>::arg1_t;
 
 
+namespace details
+{
+
+// compile-time hash for type
+// (from https://stackoverflow.com/questions/56292104/hashing-types-at-compile-time-in-c17-c2a)
+// WARNING: it does not work for unnamed struct!!!
+template <typename T>
+static consteval size_t Hash()
+{
+    size_t result{};
+
+#ifdef _MSC_VER
+    for (const auto& c : __FUNCSIG__)
+#else  // GCC and clang
+    for (const auto& c : __PRETTY_FUNCTION__)
+#endif
+        (result ^= c) <<= 1;
+
+    return result;
+}
+
+}  // namespace details
+
+template <typename T>
+static constexpr size_t mcc_type_hash = details::Hash<T>();
+
+static constexpr size_t mcc_hash_combine(size_t lhs, size_t rhs)
+{
+    constexpr size_t v_const = sizeof(size_t) >= 8 ? 0x517cc1b727220a95 : 0x9e3779b9;
+
+    lhs ^= rhs + v_const + (lhs << 6) + (lhs >> 2);
+
+    return lhs;
+}
+
+template <typename T1, typename T2>
+static constexpr size_t mcc_type_pair_hash()
+{
+    return mcc_hash_combine(mcc_type_hash<T1>, mcc_type_hash<T2>);
+}
+
 }  // namespace mcc::traits